Like super-villains, most philosophers start out with good intentions. They aim to answer big questions of general interest, like what distinguishes right from wrong or how flesh can give rise to consciousness. But they frequently end up in a baroque lair of their own making, surrounded by thought experiments which have no clear relation to the pressing issues they were meant to be addressing.
Take the time-travelling egg.
The key philosophical question is counterfactual in nature: what would have happened if someone who in fact cracked an egg into a frying pan had not done so? Let’s say it was Noam Chomsky who cracked an egg this morning. One might presume that if he hadn’t done so, he wouldn’t have eaten a fried egg for breakfast; he’d have had something else instead. Academic philosophers have raised an alternative possibility: What if Noam had eaten an egg exactly as before, except he never put it into the pan, it was just there?
Answering this question has been a matter of significant debate in philosophical journals in recent years. It has led to an investigation of how egg cooking looks if we run time backwards, Tenet style—but it’s Tenet for molecular physicists, so instead of rewinding the tape we reverse the laws of physics.
In tenure-granting work, Professor Adam Elga showed¹ how this reverse egg cracking looks at the molecular level and how, with a little jiggling of molecules, the egg cracking would never have occurred. To start, Elga considers Chomsky’s breakfast cooking in the conventional manner, from start to finish. Gravity pulls the liquid egg molecules out of the open shell, the mass of egg accelerates downwards until it hits the pan below, creating a downwards force on the pan, and an outward vibration of air waves, which we perceive as a splat sound. Next, heat from the pan is transferred into the egg molecules and the egg cooks.
Physics not only gives us the vocabulary to describe this process but shows how the sequence of events is determined: from the positions and velocities of the egg molecules at the point of cracking (along with background conditions), the laws of physics entail the precise sequence of events that will follow.
Even better, they can run in reverse. Reducing science to cliché, since every action has an equal and opposite reaction, it’s possible to work backwards, deducing the action from the reaction with complete precision. In Elga’s example, at the time at which the egg has been cooked, the velocities of the egg molecules, along with those of the pan and surrounding atmosphere determine the manner in which it was cracked. The laws of physics, if we apply them backwards, entail that the cooked egg gives up heat to the pan, thereby uncooking itself, then waves of air and vibrations of pan molecules converge on the egg, propelling it back up into the shell.
The convergence of waves required to push an egg upwards into its shell is a highly delicate process. If the position of the molecules were slightly different, the vibrational waves would not converge on the egg appropriately and would instead dissipate, leaving the egg there cooked all along. Therefore, Elga can create a scenario in which Chomsky had an egg for breakfast without ever cracking it: Take the actual world at the time the egg was cooked and jiggle the egg molecules slightly, then use the laws of physics to determine its past and future. Whereas Tenet’s improbably accented Kenneth Branaugh must reverse-detonate a nuclear bomb, if he is to destroy the world, all the philosopher-villain has to do to realize their scheme is blow onto an egg.
Though fun to imagine, this thought experiment seems a caricature of academic excess: baffling and irrelevant. It’s hard to distinguish these real-life philosophers from the protagonist in Percival Everett’s 2022 farce, Dr. No, who studies the concept of “nothing” fanatically, and, if asked whether he’s learned anything from his research, answers, “I certainly hope not.” The egg debate came about, though, from an earnest attempt to unpack the mysteries of time through questions such as why the past seems fixed while the future is open, and why causes must precede effects.
Why a question as momentous and all-encompassing as the nature of time could be thought to depend upon something as tendentious as Elga’s counterfactual scenario is puzzling. Philosophers like Elga found themselves convinced of this by following the intellectual clues step by step, each one seemingly reasonable, but the end point absurd.
The original philosophical problems with time and causality arose from Newton’s science and Hume’s imagination. Newtonian physics is symmetric regarding time—past is determined by future just as much as future by past. Newtonian laws do not provide a sense in which what happened in the past is fixed but what will happen in the future is undetermined. Even worse, relativity treats time and space as somewhat interchangeable, which makes claiming that events in the past always cause events in the future seem as arbitrary as claiming events in the north always cause events in the south. But time is the domain of physics. If it can’t distinguish past and future, what can?
Hume, meanwhile, challenged the idea that causes necessitate effects. Where we see one ball hit another, causing it to bounce off, Hume just saw a discrete sequence of events: first one ball moves in one direction, then the balls get in close proximity, then there’s a sound and the balls move in different directions. Hume imagined possibility working like Borges’ library of Babel. Just as in the library, there is a book containing every mathematically possible permutation of letters, regardless of sense or spelling. In the realm of possibility, there is a way the world could have turned out corresponding to each mathematically feasible path a set of objects could have taken through space and time. We can coherently imagine any number of paths for the balls that in fact collide, such as one flying up in the air or both vanishing entirely: there’s no necessary connection between the sequence of events that actually occur.
Academic cult hero David Lewis thought he had a way to solve these puzzles: measuring the closeness of possibilities. Just as one book in Borges’ library might share many pages with another, while a third has no commonality at all, one possible world might have a very similar sequence of events as our own, while another has no overlap. Importantly for philosophers, there is a logical system governing the closeness of possible worlds, giving them the sheen of scientific respectability—imposing some order upon Hume’s imagination.
Though virtually anything is possible, only some possibilities occur in worlds close to our own, and this underpins causality. Chomsky caused the egg to crack by tapping it on the pan, because in a possible world resembling our own in which he doesn’t tap the egg, it doesn’t crack. There are other possible worlds in which the egg cracks of its own volition, but these are much further from ours. The tragic plight of Borges’ librarians was not due simply to the library’s size but due to its disorder—the books that might aid them were buried among countless volumes of nonsense, and they had no index to guide them. Conversely, the profusion of possible worlds need not threaten causality if a structure of resemblance can be imposed upon them.
Using this structure, Lewis thought he could distinguish past and future. It’s easier to take a book and, through a slight plot twist midway through, create a completely different ending than to take the second half of a book and reverse engineer a completely different, but still coherent beginning. Similarly, Lewis argued that we can imagine worlds with an identical past to our own but, through a slight tweak, end up with a completely different future.Worlds with identical futures but divergent pasts are, however, much more far fetched.
Consider a world with an identical past to our own, up to the moment right before Chomsky cracked his egg. Then, a slight tweak occurred whereby one of Chomsky’s neurons misfired, so he changed his mind on what to eat, leading to a different future. This world resembles our own both in past events and in the general rules for how objects behave. On the other hand, it’s much harder to imagine a world with an identical future to our own post-egg-cracking but with a slight tweak to create a different past. In the future, Chomsky has a memory of turning the stove on, there is a cooked egg in the pan, an eggshell in the bin, and all kinds of other evidence that he cracked the egg then cooked it—no tweak can account for all that. That we can have possible worlds with identical pasts, small tweaks to the present and divergent futures, but not worlds with identical futures, small tweaks to the present and divergent pasts, Lewis thought, provides an explanation for why causes precede effects.
Here is where the backwards eggs speak. Adam Elga created his scenario to prove Lewis wrong. Though it’s hard to imagine a world with matching futures and diverging pasts, he argued, we don’t actually need to. All we have to do is jiggle some molecules then run the laws of physics in reverse and we are guaranteed the desired result, even if we don’t know quite how to describe it. The backwards egg scenario seems to show that when it comes to nearby possible worlds, past and future are symmetric. Just as with Borges’ library, the structuring codex that would allow us to make sense of the space of possible worlds remains hidden.
Does this mean there is no causality or that the future is not open to change? Or, do we just need to redouble our efforts at examining counterfactual eggs—perhaps quantum rather than simply molecular physics? It feels, however, like something has gone awry. The nature of time and causality don’t seem like the kind of things that should hinge on this genre of minutiae.
This narrative isn’t a one-off. Time and again, investigating an important philosophical concept in a reasonable-seeming manner draws philosophers into a maze of ever more byzantine hypotheticals.
Considerations about the nature of identity lead to interminable discussions of faulty teleportation machines. Analyzing immoral actions leads to the notorious trolley problem. Trying to understand perception leads to worries of deceiving demons and brains in vats (a scenario so ubiquitous that BIV has entered the philosophical vernacular). Descartes, like many a naïve philosopher, thought discussing his hypothetical demon was the first step in an argument that would allow him to return to his initial concerns about perception with a newfound certainty. Instead, centuries later, philosophers are discussing ever more elaborate deceivers and have given up on certainty altogether—across philosophy, the return to the big, fiery, motivating questions never happens. We remain stuck in the frying pan in perpetuity.
This isn’t meant to be a condemnation of philosophy but the presentation of a mystery. When looking at philosophers’ reasoning, there’s no clear point at which they went wrong. Wittgenstein tried to explain the universal flaw in the philosophical approach, but ended up tangled in considerations just baffling than those he was critiquing—a beetle in a box instead of an egg in a pan. Trying to answer important questions inevitably leads to an investigation of irresolvable hypotheticals that it feels like the original question could not possibly be contingent upon.
Everrett’s Dr. No reads as a farce but in a sense, it takes its subject matter incredibly seriously. It imagines a world in which philosophy is real—in which the fundamental nature of the world really does turn on the kind of scenarios philosophers dissect, so that when the protagonist thinks up a powerful enough paradox about the concept of nothingness, the entire universe is nullified. In this world, making the wrong argument about a backwards egg could cause past and future to collapse into each other—the scenario Tenet’s Protagonist fought so desperately to avoid.
Instead, we live in a world where philosophical questions function like quantum particles—behaving very weirdly when we look at them too closely, but otherwise not causing much trouble. One would think that if looking at a particle can change its very nature, when physicists started doing so, this would have some pretty significant ramifications for the physical world.It turns out, though, that once we exit the laboratory, objects continue behaving as they always have. Similarly, the fact that rigorously interrogating our world-structuring concepts confuses them to the point of nonsense would seem to undermine our ability to make sense of the world, but after putting down the philosophy book we do just fine. Neither Schrodinger’s cat nor Wittgenstein’s beetle cause problems as long as we don’t try to open their receptacles.
Where does that leave philosophers? Despite universally failing to answer the questions they set out to address, their work does keep propelling advances in other disciplines—from logic to linguistics to psychology—with uncanny regularity. Even if they’re not doing what they intend, it seems like they’re doing something. A protagonist doesn’t have to understand their story to be its hero.
- Elga, Adam. "Statistical mechanics and the asymmetry of counterfactual dependence." Philosophy of Science 68.S3 (2001): S313-S324.